The present invention relates to a solar cell containing a semiconductor body having a major surface through which light is admitted, in the proximity of which major surface a semiconductor junction is formed, a network of electrically conductive laminations bearing on the major surface and being connected to at least one collector band, the assembly of the laminations and of the band forming one of the electrodes of the cell, and the major surface being provided with grooves.
The invention relates in particular, but not exclusively, to devices having solar cells and light concentration means, in which it is possible by means of an optical system to increase the light density per surface unit area of the cells and which consequently provide larger currents than the usual devices without concentration means.
The efficiency of the light/electric current conversion of a solar cell is related in particular to the light absorption capacity of the major surface thereof: a part of the light is absorbed, while another part is reflected and is hence lost for the conversion. Besides now general use of so-called antireflection layers, which are deposited on the major surface and which reduce the reflectivity thereof, it has been proposed for increasing the absorption capacity to provide the major surface with fine grooves having a triangular cross-section so that the light which is reflected by one side of the grooves can be received by the other side, and vice versa.
An example of a solar cell having this structure is disclosed in U.S. Pat. No. 4,135,950. The wafer of silicon which is cut with a &lt;100&gt; face and is locally masked on the major surface thereof by fine parallel spaced oxide strips is subjected to a chemical etching treatment in a solution of hydrazine. In this way, parallel grooves are formed in known manner, the width and depth of which are regular, the depth being substantially equal to 7/10 of the width. A junction is formed and adjoins the surface of the grooves, and fine metal laminations are deposited on surfaces which lie on top of the teeth which are determined by the grooves, said laminations forming one of the electrodes of the cell.
Due to its groove structure said cell has a good absorption coefficient compared with that of cells having a substantially flat surface. Nevertheless, a non-negligible part of the incident light is still lost, namely that which is reflected by the fine metal electrode laminations, in spite of the considerable improvement which is provided by the grooves. The surface occupied by the laminations represents, as in any solar cell, a non-negligible part of the overall area of the major surface.